1. Field of the Invention
Embodiments of the present invention relate, generally, to an apparatus for mounting a control unit onto various stringed musical instruments.
2. Related Art
For some time, pickups that detect string vibrations have been installed on the bodies of stringed musical instruments such as guitars and the like. Also known are main control units for the pickups (hereinafter, referred to as “main control units”) that have a volume control for controlling an output level of the pickup and a connector for interfacing with a connecting cord connects that transmits the controlled signal. This kind of main control unit is mounted on the stringed musical instrument by an attachment apparatus configured such that it is possible to mount the main control unit on various stringed musical instruments.
The pickup systems marketed by the Roland Corp. under the trademarks GK-2™ and GK-3™ are examples of the system described above. These systems have a main control unit and a holder, which is the attachment apparatus for the main control unit. An explanation will be given regarding the GK-3™ main control unit and the attachment apparatus for the main control unit in reference to FIG. 8 and FIG. 9
FIG. 8 is an exterior view drawing that shows the pickup 30 and the main control unit 20. The pickup 30, which is arranged below the strings of a guitar and the like, is the divided pickup that detects the vibrations of each string independently, and the center mark 30a that is shown located in the middle of the pickup 30 is positioned in the middle of a plurality of strings. The pickup is affixed to the body of the guitar either by screwing down the pickup using screws that are inserted into the screw holes 30b that have been disposed on both ends of the pickup 30 or by sticking double sided tape on the bottom surface of the pickup 30.
The signal that is detected by the pickup 30 is input to the main control unit 20 via the pickup cable 29. The main control unit 20 is furnished with a volume control 22, an input jack 24, a toggle switch 25, a connector 23, a down switch 26, an up switch 27, and a power indicator 28.
The volume control 22 is a variable resistor that adjusts the level of the signal that has been input via the pickup cable 29. The outputs of other pickups, with which the guitar is furnished, are input to the input jack 24 via a normal guitar cable. The toggle switch 25 toggles any one of the signals that have been input to the input jack 24, the signal, the level of which has been adjusted by the volume control 22, and a signal that is a composite of the signal that has been input to the input jack 24 and the signal, the level of which has been adjusted by the volume control 22. The toggled signal is output to an external device from the connector 23.
The down switch 26 and the up switch 27 facilitate the transmission of the signal to an external device via the connector 23. The power indicator 28, which indicates that power has been supplied to the main control emit 20 when power is supplied via the connector 23, is disposed on the side of the volume control 22.
The state in which the main control unit 20 is mounted on a stringed musical instrument such as a guitar and the like is shown in FIG. 9. The main control unit 20 is configured such that the mounting on the body 60 of the stringed musical instrument is done by a holder. The holder is one that uses two holders made of metal having an “L” shape. A first holder 51 attaches to the main control unit 20 and has a first contact plate 51 a, which contacts the front surface of the body 60 of the stringed musical instrument and a first side plate 51b, which is formed perpendicular to the first contact plate 51a and contacts the side surface of the body 60 of the stringed musical instrument. A groove 51c, into which an end pin 61 is inserted, and a bolt 52 for fastening a second holder 53 are disposed on the first side plate 51b. 
The second holder 53 is configured with a second contact plate 53a, which contacts the rear surface of the body 60 of the stringed musical instrument, and a second side plate 53b, which is formed perpendicular to the second contact plate 53a and contacts the first side plate 5b of the first holder 51 running along the side surface of the body 60. A bolt 52 is formed on and extends from the side plate 5b. An elongated hole 53c, which receives the bolt 52 that has been provided on the first side plate 5b, is formed in the second side plate 53b. 
To mount the main control unit 20 on the body 60 of the stringed musical instrument, first, the main control unit 20 is attached to the first holder 51. Next, an end pin 61 of the stringed musical instrument is loosened, and the groove 51c that has been formed in the first side plate 51b of the first holder 51 is inserted on the threaded section of the end pin 61. Next, the contact plate 51a of the first holder 51 is brought into contact with the front surface of the stringed musical instrument, and the end pin 61 is tightened to fasten the main control unit 20.
Next, the bolt 52 that is provided on the first side plate 51b is inserted into the elongated hole 53c in the second side plate 53b of the second holder 53, and the contact plate 53a of the second holder 53 is brought into contact with the rear surface of the stringed musical instrument. Then, a flat washer 54 and a spring washer 55 are inserted onto the bolt 52 that is provided on the first side plate 51b, and the holder is fastened using a cap nut 56.
To remove the main control unit 20 from the body 60 of the stringed musical instrument, the cap nut 56 is loosened, and the cap nut 56, the spring washer 55, the flat washer 54, and the second holder 53 are removed from the bolt 52. Next, the end pin 61 of the stringed musical instrument is loosened, and the main control unit 20 is removed by lifting up the groove 51c of the first holder 51 along the end pin 61. The end pin 61 is, then, screwed into the body 60, returning the stringed musical instrument to a state existing before the main control unit 20 was mounted.
Bodies of conventional stringed musical instruments have been made in various shapes and with different arrangements of the volume control and the like. As a result, there have been cases in which the pickup main control unit 20 cannot be mounted on the body of the stringed musical instrument. In addition, in the past, methods such as attaching the pickup main control unit to the body of the stringed musical instrument with double-sided tape or adhesive were used. However, in many cases with these methods, the stringed musical instrument became dirty, and it was not possible to easily remove the main control unit 20.
In the methods described above, the pickup main control unit is affixed to a holder, and the holder is fastened to the body of the stringed musical instrument using the end pin of the stringed musical instrument. Because force is not applied to the body of the stringed musical instrument in the holding direction, the attachment can be weak and unstable.
In accordance with cases described above, the pickup main control unit is mounted on the body of a stringed musical instrument using a holder, and the procedure for attaching or removing the main control unit to or from the body of the stringed musical instrument is complicated.